Arrangement for tapping steam directly from double-acting reciprocating steam engines



June l2, 1934.

A. BJORKLUND 1,962,549 ARRANGEMENT FOR TAPPING STEAM DIRECTLY FROMDOUBLE ACTING RECIPROCATING STEAM ENGINES Filed March 5, 1930 ngz /nvenfon:

`Patented June 12, 1934 UNITED STATESk PATENT ori-ics Alrik Bjorklund,Gottenborg, Sweden Application March 5, 193i), Serial No. 433,447

i In Germany October 30, 1928 2 Claims. (AC1. 137-53) ,Y

This invention relates to a valve for the withdrawal of steam from thecylinders of doubleacting reciprocating steam engines during the Yexpansion stage. The object of the invention is so to construct such avalve that at every revolution ofthe crank shaft it enables two uniformwithdrawals of steam to take place, one on each side of the piston,through an outlet passage arranged at the middle of the steam cylinderl@ and uncovered from time to time by the reciprocating piston. Thewithdrawal of steam is therefore effected both during the forward`stroke and during the return stroke of the piston, always under thesame conditions as regards quantity of steam and pressure. Theregulating of the pressure at which withdrawal ceases is according tothe invention effected by axial shifting of the control piston of thewithdrawal member,

while the commencement of the withdrawal can be displaced from thecentre towards the ends of the cylinder by providing a throttling memberwhich enables the opening movement of the control piston to be retardedwhen the steam pressure is acting. In this way it is possible toregulate the quantity of steam to be tapped off, and also the withdrawalpressure, within wide limits.

In the accompanying drawing,

"r'igure 1 shows the indicator diagrams for the forward and returnstrokes, with a withdrawal of steam according to this invention;

Figure 2 shows diagrammatically in section the cylinder of areciprocating steam engine with an overflow member according to theinvention in the middle of the cylinder;

.1 Figure 3 shows one form of construction of the overflow member insection on a larger scale.

In the drawing, l is the cylinder of a reciprocating steam engine. Itmay be the high-pressure, the medium-pressure or the low-pressurecylinder as required. In the middle of the cylinder is provided anoutlet aperture 2, which is alternately covered up and uncovered by thereciprocating piston. To the outlet aperture 2 is attached an overflowmember constructed ac- `c'lording to the present invention. Thisoverflow member consists oi a casing 3 closed by a cover 4 andcontaining in a central bore a sleeve 5.

In this sleeve 5 is slidably supported a piston 7 secured to a rod 8.The piston rod'S passes in al fluid-tight manner through a positioningnut 20 screwed into the cover 4. It has at its outer end a screw thread8, upon which a plate 10 is displaceable along the rod 8. The plate 10can be clamped in position by means of a lock nut engaging with thescrew thread 8. Between the piston 7 and the positioning nut 20 isarranged a spring 6, and between the positioning nut 20 and the plate 10is arranged a spring 9.

The unloaded piston 7 is always kept in equin librium by the two springs6 and 9, independently of the initial stress applied to the springs byshifting the platelo along the piston rod 8, and

independently of the position in the casing 4 assumed by the entire unitcomprising the piston v 7, the rod 8, the springs 6 and 9 and the nut20. 5b By axially shifting the plate 10 and the positioning nut 2U thedistance :c of the lower edge ofV the piston 'i from outlet aperturesports 1l in the sleeve 5 can be made greater or smaller. This distancedetermines the amount by which the spring 6' must be compressed, andtherefore the pressure p at which the piston 7 only just closes theapertures 11 when it is exposed to the steam pressure prevailing in thecylinder with the aperture 2 uncovered. If the steam pressure is higher,75 the piston 'l uncovers the apertures, and a portion of the cylindersteam can escape through the apertures 11 and the pipe union 12 untilthe steam pressure has fallen to the value p. From the withdrawingconnection 12 the steam is then con- `veyed to the place where it is tobe used.

Above the piston 7 there is a chamber, closed in a fluidtight manner,which communicates with the withdrawal connection 12 by a by-pass 13with a shut-off cock 14 inserted therein, so that 85 the fluid enclosedin the chamber can escape when the piston 7 rises if the cock 14 isopen. rfhis device serves as a shock-absorber and a pressureequalizer.

The apparatus operates in the following manner:-

The steam supplied to the cylinder expands after the end of theadmission in the usual manner. When the piston uncovers the outletaperture 2 in the middle of the cylinder 1, steam of a pressure p passesinto the space underneath the piston 7. 1i the cock 14 is open thepiston 'l is immediately raised by the steam pressure, compressing thespring 6, so far that it uncovers the apertures 11, and a portion of thesteam can overflow through the apertures 11 into the withdrawalconnection 12 until the pressure in the cylinder has fallen to themagnitude p. The piston l then closes the apertures or ports 11 again,and the withdrawal is terminated. As mentioned above, the withdrawalpressure can be varied by axially shifting the piston '7. The withdrawalstill begins at the moment at which the piston uncovers the apertures,that is to say, in the middle of the piston stroke.

Now if the withdrawal of steam is to begin later, when the piston haspassed beyond the middle of the cylinder l, provision must be made forthe piston 7 not to open the apertures l1 suddenly but with retardation.The retardation in the movement of the piston 7 is obtained by partiallyclosing the shut-ofi cock 14, so that the piston 7, in its ascent has toovercome not only the resistance of the springs but also the adjustabledamping resistance, During the short time that the piston needs fortraversing the path a: against the damping resistance, the steam pistonhas also moved beyond the centre of the cylinder to right or left, sothat in this way, according to the adjustment of the damping resistance,the withdrawal of steam is effected correspondingly later, that is tosay, at a lower steam pressure than when the opening occurs withoutdamping resistance immediately upon the uncovering of the passage 2 bythe steam piston.

In both cases, through the same withdrawal member,'the same quantity ofsteam is drawn off in the forward stroke and in the return stroke of thepiston, at the same pressure, as a result of which smooth ruiming of theengine is ensured.

What I claim is:-

1. A valve comprising a tubular casing including a pressure chamber inits upper part and having inlet and outlet passages in its lower part,with the inlet passage in axial alinement with the bore of the casingand with the outlet passage extending across the bore; a liner seated inthe bore of the casing to separate the inlet and outlet passages fromeach other, said liner having its upper and lower ends respectivelyregistering with the pressure chamber and the inlet passage, and saidliner having ports in its intermediate part to provide communicationsbetween the interior of the liner and the outlet passage; a controllableby-pass connecting the outlet passage with the pressure chamber; and apiston slidable in the liner to control the communications through theports of the liner, a compression spring mounted in the pressure chambernormally operating to press the piston to overlap the ports, said pistonand spring being responsive to the pressure fluid entering the inletpassage of the casing to open the ports to discharge the pressure fluidfrom the inlet passage into the outlet passage and through the by-passto the pressure chamber to cushion the opening movement of the pistonand to augment the pressure of the compression spring in closing thevalve.

2. A valve comprising a tubular casing including a pressure chamber inits upper part and having inlet and outlet passages in its lower part,with the inlet passage in axial alinement with the bore of the casingand with the outlet passage extending across the bore; a liner seated inthe bore ofthe casing to separate the inlet and outlet passages fromeach other, said liner having its upper and lower ends respectivelyregistering with the pressure chamber and the inlet passage, and

vsaid liner having ports in its intermediate part to providecommunications between the interior of the liner and the outlet passage;a controllable by-pass connecting the outlet passage with the pressurechamber a piston slidable in the liner to control the communicationsthrough the ports of the liner, a positioning nut'threaded in the upperend of the casing, a rod extending through the positioning nut andattached to the piston, a main compression spring in the pressurechamber mounted on the rod between the piston and positioning nutnormally tending to press the piston to overlap the ports of the liner,said piston and spring being responsive to the pressure fluid enteringthe inlet passage of the casing to open the l ports of the liner todischarge the pressure uid from the inlet passage into the outletpassage and through the by-pass to the pressure chamber to cushion theopening movement of the piston; and to augment the pressure of the maincompression spring in closing the valve; an vadjustable abutment on theupper end of the piston rod, and an auxiliary compression spring on theupper end of the piston rod between the adjustable abutment and the topof the casing, said auxiliary compression spring normally tending tolift the piston rod and piston against the action of the maincompression spring, the adjustment of the abutment on the piston rodoperating to vary the pressure of the auxiliary compression spring to yregulate the ypressure of the main compression spring on the piston. v v

ALRIK BJORKLUND.

